1. Field of the Invention
The present invention relates to an endoscope having, at the distal end of the insertion section, a bending portion that can be bent.
2. Description of the Related Art
Endoscopes are used in medical treatment and industry. The endoscope designed for medical treatment has an elongated insertion section, which is inserted into the body cavity so that the tissues and organs in the cavity may be observed. The endoscope designed for industrial use is widely used in laying pipes and tubes in boilers, gas-turbine engines and chemical plants and in inspecting the interior of, for example, automobile engines to detect damages and corroded parts.
Most endoscopes of this type have a bending portion at the distal end of the insertion section that is to be inserted into the lumen. The bending portion can be bent. It includes a plurality of annular ring (bending segments) that are arranged in series along the axis of the insertion section. The annular rings are coupled to one another with rivets. Each annular ring is able to rotate for the adjacent annular ring. Each annular ring is a hollow member and has wire guides, which protrude inwards in the radial direction of the annular ring. Traction wires pass through the wire guides, respectively. The operation section, i.e., the proximal end of the endoscope, incorporates a bending-operation mechanism. The traction wires are coupled to the bending-operation mechanism. More precisely, the wires are connected to a bending knob provided in the bending-operation mechanism. When the bending knob is turned, the traction wires are pulled at one end, bending the bending portion upwards, downwards, leftwards or rightwards.
Jpn. Pat. Appln. KOKAI Publication No. 62-192134, for example, discloses an endoscope having a bending portion whose annular rings have a hollow with an increased sectional area. Each annular ring has wire guides that indeed lie in the hollow but do not contact the heads of the rivet. The projection protruding into the hollow of each annular ring is made as small as possible. This provides room for components and making it possible to reduce the outer diameter of the annular rings.
Jpn. UM Appln. KOKAI Publication No. 60-190301 discloses an endoscope having a bending portion. In this bending portion, the rivets coupling the annular rings (bending tubes) extend outwards in the radial direction of the insertion section. Therefore, the heads of the rivets do not project inwards in the radial direction of the annular rings. The component density is thus high in each annular ring.
Jpn. Pat. Appln. KOKAI Publication No. 2000-296103 discloses an endoscope having a bending portion. The bending portion includes a plurality of annular rings that are arranged in series along the axis of the insertion section. Each annular ring has wire guides and a bulging part that works as a rotation fulcrum. Traction wires pass the wire guides, respectively. The bulging part abuts on the next annular ring, coupling the annular ring to the next annular ring. Thus, no rivets are used to couple the annular rings. Since fastening parts, such as rivet heads project outwards or inwards of the annular ring, need not be used at all, the insertion section can be greatly reduced in diameter and the component density can be high. As a result, an endoscope having an insertion section of a small diameter can be provided.